Since the forum is called “conditions”, first a quick summary for those who don't feel like reading “novels”. Most important: the path along the Idrijca upstream to the so-called Mrak's sluices or sluices on the Idrijca is still closed due to a landslide (according to Google Streetview it was at least since last October), no idea when it will be repaired, whoever wants to get exactly to these sluices can try “attacking” them from Vojsko (with some combinatorics skills they can be connected to the Kanomelj ones) or even via marked paths from the Trnovo Forest (I think past several Golaks). But both sluices on the Belca are easily reachable without problems: Brus's and Putrih's. The circular path over Krekovše from the Lajšt swimming area at the confluence of Belca and Idrijca is easy, safe (at least as long as we don't look for “instagram” angles right at the sluices), and suitable for practically everyone, routed mostly on gravel forest roads with occasional asphalt sections, since the gravel is very good and practically without potholes, it could even be done on a road bike. Unfortunately, it's also very friendly to quads, which can dust us thoroughly at the “wrong” timing (tourist season, weekends). That's why we planned a dead-season Monday and beyond the “border of civilization” in Idrijska Bela we really didn't meet a living soul. With really bad planning (summer weekends, more below) they can also surprise us with literal Bohinj parking fees. With which the municipal fathers are just promoting “sustainable” intrusion of metal deeper into the wilderness... Surprisingly, the sluices aren't among the trips yet, which I've already fixed and it's currently awaiting approval.
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So, that was the summary, now to rambling for those who feel like reading

. Divje Lake isn't exactly technical heritage, but if it's already on the path and easily accessible, maybe even too easy… If we're precise, it's actually not a classic lake, but more like a karst spring of the shortest Slovenian river Jezernica, so something similar to the “windows” in Retovje near Vrhnika. We secretly hoped that due to recent rain and snowmelt season it would be bubbling as per the name, but… apparently you need to hurry there right after a serious heavy rain. Anyway, when we branch off in Podroteja from the main road between Idrija and Godovič, soon there's a bridge over Jezernica and right after it a small parking on the right. Since parking spots aren't marked, capacity depends on our Tetris skills. Two short paths lead to the lake, one on each bank of Jezernica, but right under the mighty wall (about 100m high I think) terrain doesn't allow either. The northern path is Vintgar-easy and could even be walked in clogs, the southern one already requires somewhat better footwear: first it crosses rock on uneven steps, and even after the terrain isn't flat. When the lake level isn't too high, you can even bypass the fence at the end of this path and get almost to the wall. The famous siphon we mortals can't see anyway. My eagle eye of a glasses-wearer

didn't spot any viewpoint on the wall above, but if anyone knows of some less official and sufficiently safe access from the old “French” road or path along the feldbahn route, I'm all ears. Just this, since space is limited, wide-angle lens is necessary for majestic immortalization, so it's worth studying a photo app on the phone in advance. And try to time the visit when there's no foliage on the trees.
From Divje Lake to Idrijska Bela the road goes approx. 6 km through a narrow gorge. Not just the gorge, the road is narrow too and in many places doesn't allow two cars to pass. On top, all blind curves and you have to watch carefully what's behind them. There are some roadside parking for a few cars, usually nearby bridges that on our side typically continue into paths up the steep bank. On the other side of Idrijca, maps suggest a walking path, up to Kobila dam a bit beyond Jezernica it's called Path by the crayfish and somehow replaces the Idrija town park, further on… given we met a runner on the road, the path probably isn't exactly suitable for that activity… If anyone knows, does it also offer similar views as from the road in the narrowest parts of the gorge?
Through Idrijska Bela we stick to the main road, then the 30 zone already indicates we're approaching Lajšt swimming area at the confluence of Belca and Idrijca. As mentioned, there are several parking lots at the swimming area that can serve as a good starting point for circular paths too. The first parking on the left was closed with a barrier, but two right after the wooden bridge over Idrijca were open. The one on the right somehow seems more natural, with an eco island too. If early morning it was somehow expected we'd be the only ones there (not even camper overnighters, who apparently aren't chased here), it's somewhat surprising our car was the only one even on return around noon. And as said, if we end up “wrong time wrong place”, it can cost us quite a bit. All parkings have a uniform fee, mostly really free, but in July and August on weekends and public holidays (Assumption 15 Aug) each hour costs exactly 3€. Or that was last year, they have time to change municipal ordinances for this year. Now consider that the sluices alone take at least 2 hours each way… Just for comparison, apparently that's the price in far more notorious Bohinj too, checked in several articles from last summer where they rant about Bohinj “usury”. Plus, payment only via some app that adds 15% commission to users. At the same time, this app tempts for 24/7 paid parking (“even if we check regularly, something falls into the till without machine operating costs and need for regular emptying”). Is there really such a rush on summer weekends (which must inevitably show on the narrow road)? At least then there's a free bus from Idrija and Črni Vrh, at least the last few years it was like that.
In the past it was probably different, hence building sluices for timber transport by water, some century ago Italians built a network of solid forest roads and thus “retired” the sluices for half a century before mining end would have done it anyway. So the path leads us all the time on fairly nice and wide roads, which at the end of Idrijska Bela recategorize from municipal to forest, mostly nice gravel without potholes, but some random asphalt sections too (hmm, if asphaltizing, isn't it more logical to start at one end and progress?). From start we go up along Belca first (in the village keep left). Since on foot and no other disturbances, more opportunities to observe surroundings, especially as the valley gets gorge attributes again and reveals channels, potholes etc. as seen through still bare trees. Not far from village a small waterfall on the other side catches attention, and perfectly a bridge before it. But looking at it doesn't inspire confidence, even before transferring my approx. 80kg net weight to the first board, doubts deepen. Hell no, not even a Peričnik is worth risking a fall several meters into shallow stream, luckily we have some optical aids for approaching, even a compact with extendable lens up to 30x optical zoom, but unfortunately surrounding trees mess with autofocus as expected, manual I'll have to learn

. “Advertises” itself also Babji zob, that's probably the lone “needle” a bit beyond that bridge. The path drags on and on, after approx. 1 hour of not “pensioner” pace from start finally. Finally Brus's or Belca sluices appear. Already from the amount of info on boards you could guess these are the “the” sluices, since closest to Idrija and they send tourists there who want to “tick off” any sluices. Even before reaching them, you can descend (very carefully!!!) somewhere along the torrent bed to a lower position for better “instagram” shots, which indeed reveal the “waterfalls” aren't even high. Otherwise you can walk across the dam to the other side, where stairs down the steep bank await. Careful again needed. Sure, fenced, but if we slip anyway (e.g. looking for photo angles), under the lower “lip” can still carry us vertically into Belca several meters below! Then more stairs bring us to a small lower space right by the water “tunnel”. How accessible in high water periods, hard to say. If we want to see sluices closer from behind too, no need to descend steep slope right behind them, better go by road another 100m, where a path branches left, gradually descends to the flat by Belca and from there almost into the “tunnel”.
Road further up along Belca soon (again) enters narrow gorge, where attention catches not a lone “needle” over left bend this time. But further can't miss pure alpine view on some vertical wall, probably Putrih or nearby peak. After approx. 25 min walk from Brus's, Putrih's sluices appear. Don't know if there was a natural waterfall here before sluices? If yes, surely a natural sight, since “waterfalls” from sluices noticeably higher than Brus's. This time I assess descent on slope before sluices too dangerous, plus trees and rocks obscure view too much for any “added value”. These sluices were supplementary and less powerful than Brus's, so description much sparser. But can descend to both tunnels via two narrow staircases (shorter ones watch heads too!). Easily find access to Belca behind sluices and thus almost to tunnel.
From here not far to Belca spring, but officially not accessible. Right after sluices road sharply turns 180° and starts climbing ridge separating Belca and Idrijca valleys. If trees not leafed yet, another nice view on sluices offers, then after approx. 20 min reach Krekovše. This is like a pass, steep slope to Vrh Bata one side, more moderate to lower Osrednik other, both obviously forested with matching “views”. On the pass itself a hamlet with few houses, first noticed on right coming from Putrih's is Krekovše hunting hut owned by namesake hunting society. No opening times data found anywhere, but tables and benches by hut, if nothing else can refresh from brought supplies.
Krekovše also kind of junction of several paths. One could take us straight to Brus's sluices (if return via Belca valley too), another shortcut to Idrijca near Lajšt, we chose longer variant on forest road, also some views, first crosses torrent bed, then after bends descends to Idrijca, briefly up along it until crossing on bridge. After bridge new fork. Left/up along Idrijca would reach sluices on Idrijca after stretched walk. But sign at fork says path passable only 1.7 km (at first glance even less than half to sluices), beyond still closed. So turn right and soon reach next sight, few meters reconstructed Idrijski Lauf, said to be world's first forest railway. When insatiable mine/ore processing needs exhausted timber along sluiced streams, forced to cut several km from rivers, so transported timber to them by “railway” or given wooden sheetmetal-clad rails better “wooden road” or “lesenica”. Tracks modular, portable to other locations, operated until sluices abolished about century ago.
Idrijca here shyly shows charms now and then, some unofficial viewpoints too. Also emerald color, could “sell” it to some as Soča

. Already before lots of picturesque torrents on steep slopes along path, when path after “lauf” after last bridge reaches right bank of Idrijca again, first warming small waterfall right after bridge, bit further really stunning cascade from top of vertical rock face to bottom. Probably occasional torrent character, else surely declared tourist sight. From there another 10 min to Lajšt or approx. 1.5 hrs from Krekovše incl. time at lauf.
Return almost no oncoming traffic too. All roadside parkings empty, surprisingly even at Divje Lake, so seize chance quick stops at some, though strictly per traffic rules not allowed (wrong side etc.). One at bridge to Strug climbing area (access to bridge requires some climbing skills already), other exactly where “feldbahn” (field railway from Godovič WWI) finally descended to road level. Path along this feldbahn route on wishlist for some time, bothered me a bit that right at Idrija end/start warnings about difficulty, which somehow doesn't match former rail routes…
When in Podroteja almost at main road junction, another “oh right!”. Luckily no sign forbids short parking by chapel under steep slope. Few meters towards Idrijska Bela maybe someone noticed steep stairs into slope. Which quickly lead to entrance of Italian “Alpine Wall” bunker from interwar. Headlamp small enough always part of obligatory gear for such explorations. Without it'd trip quick on crate inside. Inside some Italian inscriptions preserved (or someone wrote later????), coords maybe useful since GPS probably doesn't “pull” in these “cellars”

. By seen and smelled luckily no one takes literally niche labeled “latrina”, where soldiers apparently had to do business right on “čučavac”. More interesting, right by latrine stored “viveri”, which dict translates as provisions or food

. From bunker entrance fresh concreted stairs lead to steel observation dome, nearby beehive with bees not too thrilled by curious. But wait, what's that on meadow above other side of main road, surely not another bigger bunker or barracks? How come I haven't noticed till now? But fence by road itself, other question if can get closer around without disturbing property….